1. Field of the Invention
The present invention relates to a differential gear set assembling method and a differential gear set assembling device.
2. Description of Related Art
Conventionally, a differential gear set assembling device is well known as a device for assembling a differential gear set. The differential gear set includes a differential case, a pair of pinions that rotate with the differential case, and a pair of side gears that mesh with the pinions.
When the differential gear set is assembled by use of the differential gear set assembling device, the pair of side gears are placed on a top side and on a bottom side inside the differential case via coned disc springs, and a pinion temporary assembled product in which the pair of pinions are disposed at both ends of a dummy shaft is inserted into the differential case from an opening formed in the differential case, so that the pinion temporary assembled product meshes with the side gears. Subsequently, when the pinion temporary assembled product is rotated by substantially 90°, the dummy shaft is inserted into a pair of shaft holes formed in the differential case. After that, a pinion shaft is inserted into the pair of shaft holes from outside the differential case, so as to replacing the dummy shaft with the pinion shaft. Hereby, the differential gear set is finished (e.g., see Japanese Patent Application Publication No. 05-192830 (JP 05-192830 A)).
However, since the pair of side gears are biased by the coned disc springs in directions where the pair of side gears approach each other in the differential case, when the pinion shaft is inserted, the pinions receive loads from the side gears. Accordingly, at the time when the pinion shaft is inserted, the pinions are being restricted, so that a positional displacement of pinion shaft holes in the pinions, inclination (which means an inclination of an axial center of the pinion shaft hole in the pinion with respect to an insertion direction of the pinion shaft), and the like occur, which might cause poor insertion of the pinion shaft.
Further, at the time when the pinion shaft is inserted, if the pinion shaft is inserted with an excessive force, an inner diameter portion of the pinion is scratched, which causes poor quality of the pinion.
Meanwhile, it is conceivable, for example, that a device for reducing the loads from the side gears to the pinions is provided in the differential gear set assembling device separately at the time when the pinion shaft is inserted. However, in the differential gear set assembling device, a space in which to provide the device separately is narrow, so it is difficult to really provide the device. Accordingly, it is desirable to realize a mechanism for reducing the loads from the side gears to the pinions with a simple configuration in which the mechanism is provided in an existing device or mechanism in the differential gear set assembling device.